by Heinz P. Bloch
Process pump reliability logically involves a combination of fluid-related performance and design decisions that focus on engineering materials and the configuration of mechanical components. Recent case studies have pointed out improvement opportunities in the relative design conservatism found in certain process pump models. Combined with deficiencies in the training of personnel, it can be argued that pump reliability has not made as much progress as it perhaps could.
by Tom Dabbs and Dan Pereira
Hopefully you read Part 1 of “Ten Steps to Pump Reliability” and have been anxiously awaiting to read Part 2 of the article. You may get the impression that implementing these steps will be costly and very difficult to achieve. The thing you need to bear in mind is: “You are already spending the money.” The only question is: “Are you getting the result from your pumping systems that you are looking for?”
“That all important clamping force which holds the joint together – and without which there would be no joint – is not created by a good joint designer, nor by high quality parts. It is created by the mechanic on the job site, using the tools, procedures, and working conditions we have provided him with . . .”
by Alan Friedman
If you are currently running a vibration monitoring program in-house or outsourcing it to a consultant, before you potentially throw any more money in the toilet, you really need to audit your vibration monitoring program and ask yourself if you are getting any value out of it.
If you do not know what benefits you are getting from a program, you are probably not getting any benefits at all! On the other hand, if you are getting benefits but not documenting them, then your program is at risk for being cut. Either way, you need to know what is going on with your program and document it if it is good or fix it if it is not.
by John Lambert
There are so many positives involved in training your employees that you cannot lose. It’s a definite win situation for any management group. The trick is to turn it into a win/win for both you and your staff. To do this, you must choose the right training. Continue reading
By Tom Dabbs and Dan Pereira
Pump reliability is an old topic, but it is just as relevant today as it was the first time we heard it a few decades ago. There are some very good reasons to focus on improving pump reliability:
- The average annual maintenance and operations spending on centrifugal pumps is 50 percent greater than for any other type of rotating machine (FiveTwelve Group, August 2006).
- Centrifugal pumps in many plants consume more than 50 percent of total plant motor energy (Hydraulic Institute).
- Pumps consume more energy than any other class of industrial equipment (U.S. Department of Energy, 2005).
- A Finnish Research Center study of centrifugal pump performance (“Expert Systems for Diagnosis and Performance of Centrifugal Pumps,” 1996) found that the average pumping efficiency was less than 40 percent for 1,690 pumps reviewed across 20 different plants, including all market segments. The study also revealed that 10 percent of the pumps were less than 10 percent efficient.
by Jim Rowell
Last time, we pretty much ignored ladder diagrams. This time I’m giving you lots of them. We’ll look at the ins and outs of turning those pretty pictures into powerful text. You’ll gain insight into the block commands and the various structures that can be built using List. You’ll leave with full knowledge of the perils and pitfalls.
We’ll be using numbered as opposed to named I/O for the examples. Don’t get used to it and definitely don’t be discouraged by it. Numbers work best for showing you how the code works but they’re terrible at showing you what it’s actually doing. Your own code (with proper I/O names) will be much easier to follow. Continue reading
On the design of a new machine which is to be run with a hydraulic motor, a determination of required speed and horsepower must be made so a model with suitable ratings can be selected. This article describes several methods of making such a determination.
Hydraulic vs. Electric Motor Characteristics
Designers who are experienced only in selecting electric motor drives need to be careful in designing hydraulic drives because of important differences between these two motors.
Normally, an electric motor is selected on the basis of horsepower. It is selected to match an existing power source which provides constant voltage and frequency. If it happens to be a little oversize for the job, no harm is done, although it may cost a little too much. Continue reading
Hydraulic Oil Flow through Orifices
The chart shows approximate pressure drops which may be expected at various flows rates through sharp edge orifices for petroleum type hydraulic oil. It may be used for designing limiting flow orifices in hydraulic systems. Chart values must be considered as approximate because a number of factors such as specific gravity, orifice efficiency, plumbing ahead of and behind the orifice may cause variations from the values shown.
By making the orifice with a knife edge, it becomes insensitive to temperature, and the flow and pressure drop will remain the same over a reasonable range of oil temperatures (and viscosity changes).
by Henri Azibert
Fluid Sealing Association
The use of variable speed drives (VSD) has become increasingly more prevalent in an effort to improve the energy efficiency of pumping systems. Efficiency is improved through the ability of the VSD to adjust the rotational speed of a rotodynamic pump and match its hydraulic characteristics to those of the system in which it operates.
Whether the mismatch was due to the variation in required pump output or incorrect sizing of the pump, there is no question that the ability to easily vary pump speed has been a major advance in the overall performance of a pumping system. This has increased the energy efficiency, as well as the reliability of the equipment. Problems—such as
cavitation or shaft deflection—can be alleviated by running the pump at optimal system speed. But how do variable speed drives affect mechanical seals?